Thin films of MoS.sub.2 are currently the solid lubricant of choice for high precision spaceborne applications such as satellite mechanism bearings, gears, gimbals and splines. The current state-of-the-art solid lubricant films are processed by sputtering. Here, atoms are ejected from a target by bombardment with energetic particles. The ejected or sputtered particles can be condensed on the substrate to form a thin film. To obtain high purity films by sputtering, the process must be done in a vacuum, which then requires the use of radio frequency irradiation or dc electron discharge to maintain high sputter rates. The sputtering process has a number of inherent variables (e.g., target voltage, current system pressure, etc.) which make it a very complex process. Sputtering parameters must be adequately controlled to produce films with the desired properties.
Sputtered MoS.sub.2 films typically exhibit a "wormlike" morphology which is characteristic of an arrangement of MoS.sub.2 platelets that are perpendicular to the substrate surface. Such a film microstructure is sensitive to oxygen and moisture contamination which results in poor lubrications properties. Furthermore, sputtered films typically are soft and, during wear, may produce undesirable amounts of wear debris. In precision spaceborne applications, the presence of wear debris can be disastrous for device performance. These soft films also typically exhibit poor adhesion to the substrate.
The properties of thin MoS.sub.2 films grown by PLE under a variety of deposition conditions are disclosed herein.sup.1. PLE.sup.2 3 4 is a film deposition method which possesses a number of inherent advantages over conventional deposition processes such as r.f. sputtering. These advantages include congruent target evaporation, the capability of growing high purity films, and the relative ease with which many materials can be evaporated. In comparison with sputtered films, PLE-deposited films typically have superior structural properties owing to the presence of ions and other excited species in the evaporant plume. Furthermore, the inherent simplicity of PLE as compared with sputtering is another distinct advantage.
.sup.1 See also M. S. Donley, P. T. Murray, J. T. Grant, N. T. McDevitt and T. W. Hass, "Thin Solid Films", submitted for publication (not published as of filing date).
.sup.2 H. M. Smith and A. F. Turner, Appl. Opt., 4 (1965) 147.
.sup.3 B. D. Favitsanos and W. E. Sauer, J. Electrochem. Soc., 115 (1968) 109
.sup.4 H. Schwartz and H. A. Tourbellot, J. Vac. Sci. Technol., 6 (1969) 373
The tribological properties of MoS.sub.2 thin films are determined by the film stoichiometry, impurity content, morphology, crystal structure and orientation. There is a need for deposition processes which produce films with minimum contamination, especially reduced oxygen content, and optimum crystal orientation. The present disclosure details the deposition and properties of PLE-deposited thin films. X-ray photoelectron spectroscopy (XPS) was utilized to investigate film surface chemistry. Film crystal structure and orientation were examined using low angle X-ray diffraction (XRD) analysis. Coefficient of friction measurements illustrate the lubrication properties of the films.